On my '86 Lariat I am trying to wire back up the oil pressure gauge and temperature gauge. I have the wiring diagrams, but finding the wires themselves has been difficult. This truck was converted to carb, so the engine wiring harness is gone. I need to find out the path of the wires. I don't mean like the diagram, I mean if they come off the cluster and wrap above the dash or go underneath somewhere, etc. I've found them off the back of the cluster but lose track of where they go. If I can find the ends I'll be able to hook them back up.

 

I cut open the tape around wires coming from the cab into the engine bay and I found both a white/red and a red/white wire, which are the colors of the wires I'm looking for. Are these more than likely the ones I need?

 

What engine do you have?

 

Yes, those should be the wires. Put a test light on each one and, with the key on, the light should blink.

 

it's a 302

 

Okay, that's what I'm gonna try. Here's a picture of where I'm looking.

 

If they blink with the key in run, engine off, then get someone inside to monitor your gauges as you take one of those wires and ground it to the engine block. One of the gauges should move full scale. If it does it's working, the wire is good and you need to mark it "oil" or "water". Then try the other one out, it should do the same thing. Make sure the keyswitch is left in run for these tests.

 

Okay, thanks! I've tracked the wires to one plug which I will attach a picture of. I believe these are what I'm looking for.

 

This is the correct plug. The fat wire is used to power the coil positive on a DS2 IGN system.

2 of the wires are oil pressure and water temp.

The last one is a KEY ON power wire that is used for different things on different engines.

Jim

 

Okay. Well I have the gauges hooked up correctly and they are working now! I do have one more question. So when this was converted to carb somebody put in a toggle switch for the coil power and wired it that way, but I'd like to wire it back to where it's activated by the switch also. I found on a diagram that there is a wire coming out of the instrument panel that goes to the coil, but idk if it was to power the coil. Should I use the fat wire you mentioned instead?

 

What kind of ignition is in the truck now?
The fat wire is a resistor wire and only intended for the DuraSpark coil.
​​​​​​​You can use it to trigger a relay if you have HEI or something. (But be mindful it *should* have power in run, but not start)

If there is an instrument wire going to the coil it is likely dark green and is for the Tach signal.

 

I have an HEI distributor in the truck now. The toggle switch is fused I believe and it basically goes straight from the battery to the toggle, to the coil on the dist. So I'm not sure where to find the ignition wire that comes from the ignition switch. The only reason I assumed the wire coming from the instrument panel would be the one I need is because on the diagram it shows a wire coming from the ignition switch to the cluster, and then to the coil. Only wire I could find in the diagram that goes from the ignition switch to the coil.

 

If you have HEI now, you don't want to run all that current through the stock ignition switch in the dash.
Use the fat wire to trigger a Bosch style cube relay and source power directly from the hot lug of the starter relay on the fender.
Use at least 12, and maybe even 10Ga. primary wire for the feed. (10 is recommended in literature I've read)

HEI wiring has been discussed in a bunch of threads already.

 

What diagram are you looking at?

Is it for the TFI ignition that would have come in this truck when it had EFI?
If so, then you could use that wire to trigger the relay.
But idk where/why it goes through the cluster first.

I'd have to look at the schematics for fuel injected trucks.

 

This is the diagram I'm using. Yes it had EFI